Myanmar’s Parliament speaker Shwe Mann leaves after a press conference at the Union Solidarity and Development Party headquarters in Naypyitaw, Myanmar, Aug. 12, 2015

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NAYPYITAW – Myanmar’s military-backed ruling party announced the ousting of its politically popular chairman Shwe Mann hours after security forces seized the party headquarters, preventing some members from leaving.

Tensions have been building for months between President Thein Sein and Shwe Mann, who up until Wednesday’s midnight reshuffle headed the Union Solidarity and Development Party.

The men, both retired army generals, each have expressed interest in leading the country.

Candidates for the upcoming polls were announced Wednesday at an internal party meeting in the capital, Naypyitaw.

Members also were told Shwe Mann — who has lost support of the military in recent months — had been dismissed as party chair, sparking outcry by some. It was not clear if he will stay on as the influential speaker of parliament.

“I heard something is going on with the changing of party leaders or high-ranking offices,” Minister of Information Ye Htut said on his Facebook page, adding there was little more he could say as it was a party matter.

The surprising development has for the first time given an indication to Myanmar people that the military-backed ruling party, which had long been seen as a monolithic and united institution, is not without petty politics, fractures and power plays. It should also boost the opposition party, whose clout has only been increasing rapidly ahead of the elections.

Myanmar only recently began transitioning from a half-century of dictatorial rule to democracy.

The Nov. 8 general elections will be the first since a nominally civilian government was installed in 2011. But with the military still firmly in control of the process, there has been widespread speculation as to whether they will be free and fair. Opposition leader Aung San Suu Kyi, who enjoys huge public support, is barred from running for president but is seeking re-election to Parliament.

Shwe Mann was seen as a leading candidate for the presidency.

The party said at a brief news conference Thursday he was being replaced by the party’s vice-chairman Htay Oo.

No clear explanation was given.

Witnesses said trucks started arriving at the USDP headquarters on Wednesday night. Soldiers and police were seen entering the building and some party members were prevented from leaving, though by Thursday afternoon only a few police were deployed at the gate of sprawling compound.

Thein Sein was handpicked by former dictator Than Shwe and has retained the support of the armed forces despite implementing some reforms, including the freeing up of the media and the release of political prisoners — though there have been hundreds of new arrests under his watch.

He was holding an emergency meeting with Cabinet members Thursday.

Shwe Mann’s relationship with the military, meanwhile, has deteriorated steadily in the last year.

Seen as a reformist, and an ally of Suu Kyi, he was accused by military MPs recently of creating “misunderstandings” between the public and the armed forces.

That followed his support for a call in parliament to amend Article 436 of the Constitution, which gives the military the power to veto all amendments.

A witness said Shwe Mann’s home security official was seen being questioned by the chief of police. Not seen publically since the news, he was believed to be inside.

“My father is right now at his home in Naypyitaw with the security guards,” said Toe Naing Mann, Shwe Mann’s son. “I don’t know whether he is allowed to go out or now.”